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Ongoing project

Management of insecticide resistance in serpentine leafminer (Liriomyza huidobrensis) (AS20002)

Key research provider: NSW Department of Primary Industries

What's it all about?

This investment is developing accurate, cost-effective surveillance tools that can be used to monitor insecticide resistance in serpentine leafminer (SLM). With the knowledge generated by this project, a sustainable integrated pest management approach for the pest can be established with the aim to reduce the impact of serpentine leafminer in horticultural crops.

Serpentine leafminer is a newly introduced exotic pest to Australia with the potential to seriously damage Australian horticultural nursery and vegetable industries including onion, potato and sweetpotato. The pest is controlled by insecticides, but at present nothing is known about chemical efficacy or potential insecticide resistance.

The research team will begin by establishing baseline resistance data from at least three strains of serpentine leafminer collected from NSW and Queensland. This is the first tool for resistance detection when resistance mutations are unknown. Next, populations of serpentine leafminer from Queensland will be included into the resistance testing and field trials against dimethoate, imidacloprid and spirotetramat will be undertaken.

At the same time, whole genome sequencing of serpentine leafminer will be carried out as the crucial first step towards a complementary DNA-based resistance detection capability for the pest. The research team will use cutting edge genomic methodology to build a serpentine leafminer genome for use by Australian researchers.

This investment will work closely with the project Management strategy for serpentine leafminer, Liriomyza huidobrensis (MT20005).

The project team report the following:

  • Serpentine leafminer (SLM), Liriomyza huidobrensis strains tested in this study were collected from Australian vegetable growing regions of Queensland and NSW.
  • Two strains, Riley-2 and Kemp C from NSW and one strain, Wereema-2021 from Queensland were tested for insecticide response against dimethoate, imidacloprid, spirotetramat, and chlorantraniliprole.
  • Dose response and DNA-based testing suggest resistance to all above chemicals is likely.
  • No resistance-causing point mutation to the Group 5 Spinosyns (e.g. Spinetoram, Spinosad) was found suggesting they could be trialed against SLM.
  • Baseline dose response for these three SLM strains against dimethoate and imidacloprid showed a similar and potentially resistant type response between strains with rates required to achieve 100% mortality significantly higher than the recommended field rate (as set by the manufacturer). LC50 estimates ranged from 1.4 (95% fiducial limit (FL) 0.8-2.0) to 2.5 (95% FL 2.1-3.0) g / L for dimethoate and from 1.8 (95% FL 1.0-2.8) to 2.0 (95% FL 1.7-2.4) g / L for imidacloprid. Baseline dose responses against spirotetramat and chlorantraniliprole are in progress.
  • Similarly, single field rate responses for these three SLM strains against spirotetramat and chlorantraniliprole suggest resistance may have developed as less than 100% mortality was achieved, but the full dose-response data are required for confirmation.
  • Molecular resistance screening via multilocus amplicon sequencing and whole genomic sequencing resulted in the following resistant alleles being detected:
  • Carbamate/organophosphate: + I129V and G227A conferring resistance to Group 1A Carbamates (e.g. Methomyl, Carbaryl) and Group 1B Organophosphates (e.g. Chlorpyrifos, Dimethoate, Trichlorfon)
  • Pyrethroid: + Super kdr resistant alleles, M918T and L1014F, conferring resistance to Group 3A Pyrethroids (e.g. Bifenthrin, Permethrin, Alpha-cypermethrin, Zeta-cypermethrin, Cyhalothrin)
  • Phenylpyrazoles: +A301S mutation conferring resistance to Group 2B Phenylpyrazoles (e.g. Ethiprole, Fipronil)
  • Diamides: + I4790M mutation conferring resistance to Group 28 Diamides (e.g. Chlorantraniliprole, Cyclaniliprole, Cyantraniliprole)
  • All tested SLM populations were homozygous resistant for these point mutations.
  • Concurrently, molecular resistance screening via multilocus amplicon sequencing and whole genomic sequencing has detected no mutations associated with the Group 5 Spinosyns (e.g. Spinetoram, Spinosad), Group 6 Avermectins (e.g. Abamectin) or the Group 10B (e.g. Etoxazole) insecticides.